Key Points

Targeted cancer therapies use drugs that block the growth and spread of
cancer by interfering with specific molecules involved in carcinogenesis (the
process by which normal cells become cancer cells) and tumor growth (see
Questions 1, 2, and 3).

Because scientists call these molecules “molecular targets,” therapies that
interfere with them are sometimes called “molecular-targeted drugs,”
“molecularly targeted therapies,” or other similar names (see Question 1).

The National Cancer Institute's Molecular Targets Development Program is
working to identify and evaluate molecular targets (see Question 6).

1. What are targeted cancer therapies?

Targeted cancer therapies use drugs that block the growth and spread of
cancer. They interfere with specific molecules involved in carcinogenesis (the
process by which normal cells become cancer cells) and tumor growth. Because
scientists call these molecules “molecular targets,” these therapies are
sometimes called “molecular-targeted drugs,” “molecularly targeted therapies,”
or other similar names. By focusing on molecular and cellular changes that are
specific to cancer, targeted cancer therapies may be more effective than
current treatments and less harmful to normal cells.

Most targeted cancer therapies are in preclinical testing (research with
animals), but some are in clinical trials (research studies) or have been
approved by the U.S. Food and Drug Administration (FDA). Targeted cancer
therapies are being studied for use alone, in combination with each other, and
in combination with other cancer treatments, such as chemotherapy.

2. What are some of the cellular changes that lead to cancer?

Normally, cells grow and divide to form new cells as the body needs them.
When cells grow old, they die, and new cells take their place. Sometimes this
orderly process goes wrong. New cells form when the body does not need them,
and old cells do not die when they should. These extra cells can form a mass of
tissue called a growth or tumor. The cells in malignant (cancerous) tumors are
abnormal and divide without control or order. They can invade and damage nearby
tissues and organs. Also, cancer cells can break away from a malignant tumor
and spread to other parts of the body.

Normal cell growth and division are largely under the control of a network
of chemical and molecular signals that give instructions to cells. Genetic
alterations (changes) can disrupt the signaling process so that cells no longer
grow and divide normally, or no longer die when they should. Alterations in two
types of genes can contribute to the cancer process. Proto-oncogenes are normal
genes that are involved in cell growth and division. Changes in these genes
lead to the development of oncogenes, which can promote or allow
excessive and continuous cell growth and division. Tumor suppressor
genes are normal genes that slow down cell growth and division. When a
tumor suppressor gene does not work properly, cells may be unable to stop
growing and dividing, which leads to tumor growth.